1. Field of the Invention
The present invention relates to a heat treatment installation comprising UHF or microwave heating means for the processing of parts made of a composite material with a ceramic matrix. The invention also relates to the treatment of such parts using the installation.
2. Discussion of the Background
As used herein, UHF waves, or microwaves, are Hertzian waves with frequencies below 300 GHz, a standard frequency currently used being 2.45 GHz.
The advantages obtained by the use of microwave heating in various applications are well known, namely:
absence of thermal inertia, since the release of heat is restricted to the time for which the radiation source is in operation; PA1 direct heating inside the articles to be heated without affecting the environment (i.e. the enclosure or gas atmosphere around the article) and without overheating the surfaces; PA1 improvement of heating homogeneity for a homogeneous product and the possibility of selective heating in the case of a heterogeneous product. PA1 a treatment enclosure, PA1 a UHF or microwave generator, PA1 a waveguide for conducting waves generated by said generator into said treatment enclosure, PA1 a die in said treatment enclosure for receiving a part to be treated, PA1 means for single-axis hot pressing said part placed in said die in said enclosure, and PA1 means for introducing a neutral gas, such as argon, into said treatment enclosure for protecting said part during treatment. PA1 setting up the part to be treated on a support inside the treatment enclosure, setting up heat protection screens around the part, and closing the enclosure; PA1 introducing a protective inert gas into the enclosure; PA1 operating the microwave generator to microwave heat the part to a temperature above 1000.degree. C., the temperature being selected according to the material forming the part; PA1 simultaneously operating the single-axis pressing means integrated with the enclosure to press the heated part; PA1 stopping the heating; PA1 releasing and removing the part from the enclosure.
Known installations for carrying out heat treatments using microwaves as the heating means generally comprise a radiation source or UHF wave generator which converts the electrical energy of the power supply into microwave energy, the generator usually being of the magnetron type, a treatment enclosure, an adaptor situated between the generator and the enclosure which acts as an impedance transformer for ensuring a satisfactory output, and waveguides connecting the different parts.
Examples of such arrangements are disclosed, in particular, in FR-A-2 390 025, FR-A-2 423 875, FR-A-2 523 797 and FR-A-2 606 577, which describe various applications for using the apparatus.
However, no fully satisfactory solution has been proposed for the production of parts made of a composite material having a ceramic matrix calling for, in particular, treatment cycles at high temperatures, especially in excess of 1000.degree. C. Such requirements are met particularly in the production of parts intended for aero-engines.